FIELD OF THE INVENTION
The invention lies in the automotive technology field. More specifically, the invention relates to a device and a method for sensing an object or a person in the interior of a vehicle.
Persons who are displaced far forward in the direction of the dashboard such as, for example, children and infants in so-called rearward facing child seats on the front-seat passenger seat are subjected to the hazard, during the operation of a motor vehicle provided with an airbag, of suffering injuries as result of the inflation impact of the airbag in the event of an accident. Modern control systems for person protection aim at switching off the airbag in such situations or inflating it with reduced momentum in order to avoid the risk of injury to a vehicle occupant. In order to determine the position of the vehicle occupant in the vehicle, use is preferably made of contactless, optical sensors.
A device for the contactless detection of an object or of a person in the interior of a vehicle is known from European patent application EP 0 669 227 A1. There, the vehicle seat is irradiated by a number of LEDs. Beams which are reflected from the seat or a person or an object on the vehicle seat are registered by a photodetector field.
Such a device for detecting objects and persons is usually arranged in the interior of the vehicle as a device which is embodied separately from the actual control device for the occupant protection means, in such a way that it is made possible either for a vehicle occupant to be detected on the vehicle seat or else for a hazard zone to be sensed in front of the folded-up airbag. In the latter case, the interior of the vehicle, or at least part of it, is preferably examined for the presence of an object or of a person. If a child's seat or part of a body of a vehicle occupant is detected in this hazard zone, the airbag is not triggered, or is only triggered in a metered fashion.
The device is operated with a power supply. In the event of an impact in which in particular the position of a vehicle occupant must be detected in order to be able to influence the unfolding of the airbag if necessary, it is then possible to interrupt the power supply to the device by way of a mechanical effect, or to adversely affect the power supply in the form of a power leakage discharge, in such a way that the supply voltage which is necessary to operate the electrical device can no longer be permanently ensured. Thus, in the event of an impact, there is the risk of the device being operationally incapable exactly during the decisive milliseconds during the impact. Even if the power supply is still intact with a reduced supply voltage, the device is no longer capable of registering the necessary data and outputting it to a control device for the occupant protection means because the device usually contains loads with a high power requirement, such as laser diodes, for example.